Create number grid of text objects in Animation Nodes
Well it seems that I've answered my own question.

My mistake was using a source text object for the instancer. Instead, I just disabled the "Copy from source" setting and then selected "Text" from the drop down list of available types to instance.



The next challenge will be getting the numbers to count up horizontally instead.

Update!

I vastly simplified the node network from my (deleted) post yesterday, and made it able to order the numbers in anyway you want, up down left right, down up right left, etc.



There's still just the issue of not having any access to the font object material at all.